The larvae of the peach twig borer are off white with a defined black head. As the peach twig borer larvae mature, they darken to a chocolate brown with alternating dark and light bands around the abdomen. The light, intersegmental membranes contrasted with the brown body distinguish the peach twig borer larvae from other types of larvae found in stone fruits. Mature larvae are about 0.5 inch long and pupae are 0.25 to 0.4 inch long. Pupae are brown in color and they do not have a cocoon. Pupation may occur in the stem cavity of infested fruit or it may occur in shielded sections of the tree.
Once the larvae mature the peach twig borer can damage stone fruits by feeding in shoots and causing shoot strikes. They may also feed directly on the fruit. When the peach twig borer attacks young, developing trees, shoot damage can be severe. Hungry borers feed so vigorously that they end up killing the terminal growth. This results in undesirable lateral branching.
There are several ways to manage peach twig borer infestations. You may use timed treatments of insecticides such as Bacillus thuringiensis, spinosad (Entrust, Success), methoxyfenozide (Intrepid), and diflubenzuron (Dimilin). Mating disruption with sex pheromones is also useful. Biological control is effective as the peach twig borer has 30 species of natural enemies such as the gray field ant. This ant preys on the peach twig borer during the spring and summer months.
If you are interested in organic methods of peach twig borer control, look no further than bloom time Bacillus thuringiensis sprays, sprays of the Entrust formulation of spinosad, and mating disruption. These are all organically acceptable methods for peach twig borer control.
Sources: University of California Agriculture and Natural Resources
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